Cinétique de dégagement des matières volatiles lors de la pyrolyse d'électrodes de carbone industrielles

In aluminium plants, the anode baking process is associated with an important release of volatile combustible matter. It is the purpose of this study to investigate the kinetics of the evolution of these volatiles. A large thermogravimetry set-up has been designed in such a way that it could simulate real plant conditions. Samples of two distinct masses have been subjected to pyrolysis at different heating regimes. The loss of weight together with the concentrations of the released gases were recorded on a continuous basis during the temperature rise. Kinetic results were found for methane, hydrogen and tar. No variation of the order of reaction with the heating rate was observed, whereas the activation energy and the pre-exponential factor increased. Furthermore, for the range of sample dimensions studied, it was found that the mass of the solid had no significant influence on the kinetic parameters.     

Concentration and temperature dependence of plasticizer diffusion into plasticized PVC

The diffusion of a plasticizer S₁ from a source made of PVC containing 25 wt% of S₁ into a medium made of PVC film containing another plasticizer S₂ in 15, 20, 25 and 30 wt%, was studied at temperatures ranging from 70 to 108°C. S₁ was generally diphenyl-iso-octyl phosphate (DPIP) and S₂ was dioctyl phthalate (DOP) but the reciprocal system was also studied in some cases. Starting from a reference point corresponding to a temperature of 70°C and a DOP concentration of 25 wt%, it was found experimentally that an increase Δv of the DOP volume fraction (v) or an increase ΔT of the temperature, led to the same variation of the diffusion coefficient of DPIP if ΔT/Δv ～ 139K. A reasonably close value can be obtained from a simple free-volume approach, using the literature data on the plasticizer action of DOP on PVC.     

Evaluation of the Nonuniformity of Filaments Based on Data from Pulsed-Acoustic Tests of Complex Chemical Fibres

The values of the elongation at break of filaments in a complex fibre are found by the method of combining the stress-strain diagrams and acoustic emission spectra of fracture of complex fibres. Experimental data are used to assess the correspondence of the empirical law of distribution of the elongation at break of filaments to the theoretical (normal) law. The behavior of filaments in extension of a complex fibre to breaking is described with the concepts of reliability theory and the statistical indexes characterizing the nonuniformity of the filaments and the working capacity of a complex fibre in elongation close to the elongation at break are calculated. Complex fibres fabricated by melt spinning (polyester, polypropylene) have higher reliability reserves than fibres wet-spun from solution (viscose). The results are of practical importance and can be used for optimizing industrial manufacture and processing of complex fibres.     

Dependence of spall strength of metals on the amplitude of a shock-wave load

Arzamas. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 1, pp. 94–98, January–February, 1992.     

Scale effect in high-rate (spall) failure

Experimental results on the spall strength of copper in which the scale of the system was changed by a factor of ten show that the scale effect for high-rate one-dimensional strain depends on energy. The spall energy per unit surface area for failure increases with time. Arzamas-16. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 88–93, November–December, 1993.     

Synthesis of boronate-containing copolymers of N,N-dimethylacrylamide, their interaction with poly(vinyl alcohol) and rheological behaviour of the gels

Cross-linking of polyvinylalcohol (PVA) by boronate-containing copolymer of N,N-dimethylacrylamide (DMAA, 1) was studied and compared to cross-linking of PVA by borate buffers in weakly alkaline solutions. The copolymer of M_w=19,000 g mol⁻¹ containing 9 mol% N-acryloyl-m-aminophenylboronic acid (NAAPBA, 2) was prepared by free radical polymerization of the monomers, exhibiting copolymerization constants r₁=0.84 and r₂=2.2. Due to multipoint interaction of the copolymer with PVA via monodiols, the intermolecular cross-linking required for seven-fold and 10-fold lower boron concentrations as compared to borate buffers of pH 8.6 and 7.5, respectively. In rheological measurements, PVA-copolymer gels exhibited storage moduli (G′_max) comparable to those of PVA-borate gels prepared at 7.5-fold higher boron concentration and the same pH 8.6, what testified to the similar concentration of cross-links in the gels. Therefore, DMAA-NAAPBA copolymer is a more effective cross-linker of PVA than borate. The PVA-copolymer gel exhibited much higher relaxation time (97 s) compared to PVA-borate gels (≤20 s) indicating a longer lifetime of junction zones. The ‘shape stability’ of the gel is suggested to originate in the structure of junctions, containing several boronate-diol complexes, between the macromolecules of PVA and the copolymer.     

Flux pinning effect of cubic equiaxed morphology and its Ti stabilizing in Nb<Subscript>3</Subscript>Sn superconductors

Two sets of internal-Sn Nb3Sn superconducting strands were fabricated through RRP method, one with 2 wt% of Ti alloyed in Sn core and the other just pure Sn. Four reaction temperatures of 650℃, 675℃, 700℃ and 725℃ and 128 h duration were applied for A15 phase formation heat treatment after Cu-Sn alloying procedure of 210℃/50 h + 340℃/25 h. For the heat-treated coil samples, transport non-Cu JC was examined through standard 4-probe technique and phase microstructure was observed by means of Field Emission Sc...     

The Concept of Chamber Design for Explosive Thermonuclear Fusion Energetics

The possibility of realizing the solution of mankind's energy problem by the explosive thermonuclear fusion method that was proposed by Academician A. D. Sakharov is assessed. The essence of the method consists of the use of the energy of low–power thermonuclear explosions performed cyclically in stationary explosion–proof chambers equipped with a means for selection and utilization of the thermal energy of the explosion. Here the basic problem is to design airtight chambers capable of withstanding multiple thermonuclear explosions whose power is equal to 10—25 ktons of TNT. The available data on this problem are examined. The concept of designingreliable explosion–proof chambers for the solution of the indicated problem is formulated.